Currently, most of the X-ray light sources used in real-time containers/vehicle scanning and imaging systems are produced by linear electron accelerators having constant output dose rates. In general, imaging technical indexes of an inspection system, especially system penetrability, depends on the output dose rate of its accelerator, i.e., the higher the dose rate is, the better the penetrability is. However, since X-ray may cause radiation damage to human bodies and the environment, it is necessary to control the accelerator output dose rate in operation, or provide additional shielding protection or other measures, to meet the requirement of the environmental dose level.
In order to meet the requirements for scanning under various different conditions, the accelerators' dose rates and energy levels of imaging systems are usually set to their maximum penetration and material resolution setting values that are allowed by the systems. However, in actual situation, the cargoes under inspection or the amounts of cargoes carried by containers/vehicles are usually different, so, the requirements of X-ray output dose rates and energy levels for a particular scan imaging system may vary greatly, which may cause a dose rate above an actually required value in scanning, additional shielding protection cost, or unnecessary radiation to relevant operators. If a suitable accelerator dose rate or electron beam energy level may be selected according to actual situations of cargoes to be inspected, an imaging inspection system that may guarantee satisfied system imaging technical indexes and image quality without causing unnecessary cost for radiation shielding protection may be realized, which has important practical significance.
There is a technique in the prior art for imaging different regions of an object to be inspected using a multi-dose and multi-energy accelerator, which mainly relates to a fast inspection system, for example, a head region of a vehicle where the driver locates may be scanned at a lower safety dose rate which may not cause damage to the driver, and a cargo region of the vehicle may be scanned at a higher dose rate. This scheme has gained successful applications in X-ray fast inspection system devices, however, it cannot be adjusted according to varied situations of cargoes, and thus has certain limitation.